Narrow cast and wide cast in ABAP OO

Question

Hi Xperts
Considering the code below can the concepts of narrowing cast and widening cast be explained ? Kindly help me in getting a clear picture of the usage of it.
CLASS C1 DEFINITION.
  PUBLIC SECTION.
    CLASS-DATA: COUNT TYPE I.
    CLASS-METHODS: DISP.
ENDCLASS.                    "defintion  C1
CLASS C1 IMPLEMENTATION.
  METHOD DISP.
    WRITE :/ COUNT.
  ENDMETHOD.                    "disp
ENDCLASS.                    "c1 IMPLEMENTATION
CLASS C2 DEFINITION INHERITING FROM C1.
  PUBLIC SECTION.
    CLASS-METHODS: GET_PROP.
ENDCLASS.                    "c2  INHERITING C1
CLASS C2 IMPLEMENTATION.
  METHOD GET_PROP.
    COUNT = 9.
    CALL METHOD DISP.
  ENDMETHOD.                    "get_prop
ENDCLASS.                    "c2 IMPLEMENTATION
START-OF-SELECTION.
  DATA: C1_REF TYPE REF TO C1,
        C2_REF TYPE REF TO C2.
PS: Pls dont post any links as i already gone thru couple of those in SDN but couldnt get a clear info

Answer 1

Hi
I got to know abt narrow cast: referecing a super class ref to a subclass ref so that the methods in subclass can be accessed by the super class reference. Below is snippet of the code i'd checked. Hope this is correct to my understanding. If any faults pls correct me. Also if anyone can explain wideing cast in this context will be very helpful
FOR NARROW CAST
{size:8}
CLASS C1 DEFINITION.
  PUBLIC SECTION.
    CLASS-DATA: COUNT TYPE I.
    CLASS-METHODS: DISP_COUNT.
ENDCLASS.                    "defintion  C1
CLASS C1 IMPLEMENTATION.
  METHOD DISP_COUNT.
    WRITE :/ 'Class C1', COUNT.
  ENDMETHOD.                    "disp
ENDCLASS.                    "c1 IMPLEMENTATION
CLASS C2 DEFINITION INHERITING FROM C1.
  PUBLIC SECTION.
    CLASS-METHODS: GET_PROP,
                   DISP.
ENDCLASS.                    "c2  INHERITING C1
CLASS C2 IMPLEMENTATION.
  METHOD GET_PROP.
    COUNT = 9.
    CALL METHOD DISP.
  ENDMETHOD.                    "get_prop
  METHOD DISP.
    WRITE :/ 'Class C2', COUNT.
  ENDMETHOD.                    "DISP
ENDCLASS.                    "c2 IMPLEMENTATION
START-OF-SELECTION.
  DATA: C1_REF TYPE REF TO C1,
        C2_REF TYPE REF TO C2.
  CREATE OBJECT: C2_REF TYPE C2.
*  CREATE OBJECT: C1_REF TYPE C1.
  BREAK-POINT.
  C1_REF = C2_REF.
  CALL METHOD C1_REF->DISP_COUNT.
  CALL METHOD C1_REF->('GET_PROP').
{size}
Edited by: Prabhu  S on Mar 17, 2008 3:25 PM